US2978368A - Corrosion inhibition in ferrous metals - Google Patents

Corrosion inhibition in ferrous metals Download PDF

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Publication number
US2978368A
US2978368A US746328A US74632858A US2978368A US 2978368 A US2978368 A US 2978368A US 746328 A US746328 A US 746328A US 74632858 A US74632858 A US 74632858A US 2978368 A US2978368 A US 2978368A
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Prior art keywords
ferrous metal
nitride
metal plate
layer
opposite surface
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US746328A
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Horsley Geoffrey Winton
Frost Brian Reginald Thomas
Maskrey John Thomas
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UK Atomic Energy Authority
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UK Atomic Energy Authority
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    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C10/00—Solid state diffusion of only metal elements or silicon into metallic material surfaces
    • C23C10/18—Solid state diffusion of only metal elements or silicon into metallic material surfaces using liquids, e.g. salt baths, liquid suspensions
    • C23C10/20—Solid state diffusion of only metal elements or silicon into metallic material surfaces using liquids, e.g. salt baths, liquid suspensions only one element being diffused
    • C23C10/22—Metal melt containing the element to be diffused
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23F—NON-MECHANICAL REMOVAL OF METALLIC MATERIAL FROM SURFACE; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL; MULTI-STEP PROCESSES FOR SURFACE TREATMENT OF METALLIC MATERIAL INVOLVING AT LEAST ONE PROCESS PROVIDED FOR IN CLASS C23 AND AT LEAST ONE PROCESS COVERED BY SUBCLASS C21D OR C22F OR CLASS C25
    • C23F11/00—Inhibiting corrosion of metallic material by applying inhibitors to the surface in danger of corrosion or adding them to the corrosive agent

Definitions

  • the present invention relates to corrosion inhibition of ferrous metals in contact with liquid metals, for example, bismuth.
  • nitride formers It is known to protect steel vessels containing liquid meta s by dissolving substances such as zirconium and titanium, known as nitride formers, in the liquid metals.
  • the nitride formers combine with nitrogen in the steel to form a corrosion resistant layer of nitride on the steel.
  • this layer is apt to flake off in the course of time, producing gaps in the protective layer in which.
  • a method of inhibiting corrosion of one surface of a ferrous metal plate when said surface is in contact with a liquid metal containing a nitride former comprises forming a layer of a nitride of the ferrous metal on the opposite surface of said plate.
  • the nitrogen ions in this layer migrate through the ferrous metal to its interface with'the liquid metal, combine with the nitride former and so the protective layer of nitride is renewed.
  • the layer may be formed and continuously replenished by feeding ammonia continuously to said opposite surface if the ferrous metal is maintained at a temperature of 500 C.600 C.
  • 'a jacketed steel vessel contained liquid bismuth to which had been added 500 p.p.m. of zirconium and 500 p.p.m. of calcium.
  • the calcium acted as a getter of any non-metallic impurities, such as oxygen and chlorine, in the bismuth which might react with the zirconium.
  • the steel of the vessel was 2%% Crl% Mo superheated steel about .064 in. thick and the bismuth was more than 99.99% pure. Both the zirconium and the calcium were more than 99.0% pure.
  • the vessel was heated by electric heating elements to maintain the bismuth at 550 C. and dry ammonia was supplied to the jacket, a small bleed ensuring that the ammonia was completely replaced by fresh ammonia about every 24 hours.
  • the interior surface of the vessel was polished and the exterior, within the jacket, was shot-blasted.
  • a method of inhibiting corrosion of a ferrous metal plate containing nitrogen and having a surface in contact with a liquid metal comprising adding to the liquid metal an element which combines with the nitrogen in the ferrous metal plate to form a corrosion resistant nitride layer on said surface, contacting the opposite surface of the ferrous metal plate with a material which forms a nitride of the ferrous metal, and maintaining a layer of the ferrous metal nitride on said opposite surface during the time said liquid metal is in contact with the ferrous metal plate, whereby nitrogen ions migrate from said opposite surface to said first-named surface to maintain the nitride layer on said first-named surface.
  • a method according to claim 2 wherein said element added to the liquid metal is selected from the group consisting of zirconium and titanium.
  • liquid metal is bismuth

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Solid-Phase Diffusion Into Metallic Material Surfaces (AREA)
  • Preventing Corrosion Or Incrustation Of Metals (AREA)

Description

United Stat Patent CORROSION INHIBITION 1N FERROUS METALS Geoffrey Winton Horsley, Wantage, and Brian Reginald Thomas Frost and John Thomas Maskrey, Abingdon, England, assignors to United Kingdom Atomic Energy Authority, London, England No Drawing. Filed July 3, 1958, Ser. No. 746,328
Claims priority, application Great Britain July 3, 1957 4 Claims. (Cl. 14816.6)
The present invention relates to corrosion inhibition of ferrous metals in contact with liquid metals, for example, bismuth.
It is known to protect steel vessels containing liquid meta s by dissolving substances such as zirconium and titanium, known as nitride formers, in the liquid metals. The nitride formers combine with nitrogen in the steel to form a corrosion resistant layer of nitride on the steel. Unfortunately, this layer is apt to flake off in the course of time, producing gaps in the protective layer in which.
pitting of the steel occurs. The gaps are not readily self-healing since the nitrogen in the steel available for combination with the nitride former becomes exhausted.
It is an object of the present invention to provide a method of corrosion inhibition whereby said corrosionresistant nitride layer is substantially self-healing.
According to the present invention a method of inhibiting corrosion of one surface of a ferrous metal plate when said surface is in contact with a liquid metal containing a nitride former comprises forming a layer of a nitride of the ferrous metal on the opposite surface of said plate.
The nitrogen ions in this layer migrate through the ferrous metal to its interface with'the liquid metal, combine with the nitride former and so the protective layer of nitride is renewed. The layer may be formed and continuously replenished by feeding ammonia continuously to said opposite surface if the ferrous metal is maintained at a temperature of 500 C.600 C.
In an example, 'a jacketed steel vessel contained liquid bismuth to which had been added 500 p.p.m. of zirconium and 500 p.p.m. of calcium. The calcium acted as a getter of any non-metallic impurities, such as oxygen and chlorine, in the bismuth which might react with the zirconium.
ice
The steel of the vessel was 2%% Crl% Mo superheated steel about .064 in. thick and the bismuth was more than 99.99% pure. Both the zirconium and the calcium were more than 99.0% pure.
The vessel was heated by electric heating elements to maintain the bismuth at 550 C. and dry ammonia was supplied to the jacket, a small bleed ensuring that the ammonia was completely replaced by fresh ammonia about every 24 hours.
The interior surface of the vessel was polished and the exterior, within the jacket, was shot-blasted.
After 17 weeks the vessel was emptied and the inner surface examined microscopically. Some pitting corrosion had occurred but the pits had been sealed-off by the growth of a new film.
An experiment with a similar vessel to which no ammonia was supplied resulted in severe pitting corrosion and no growth of new film.
We claim:
1. A method of inhibiting corrosion of a ferrous metal plate containing nitrogen and having a surface in contact with a liquid metal, comprising adding to the liquid metal an element which combines with the nitrogen in the ferrous metal plate to form a corrosion resistant nitride layer on said surface, contacting the opposite surface of the ferrous metal plate with a material which forms a nitride of the ferrous metal, and maintaining a layer of the ferrous metal nitride on said opposite surface during the time said liquid metal is in contact with the ferrous metal plate, whereby nitrogen ions migrate from said opposite surface to said first-named surface to maintain the nitride layer on said first-named surface.
2. A method according to claim 1 wherein said opposite surface of the ferrous metal plate is contacted with ammonia and the ferrous metal nitride layer is maintained by continuously feeding ammonia to said opposite surface while the temperature of the ferrous metal plate is maintained at about 500-600? C. r
3. A method according to claim 2 wherein said element added to the liquid metal is selected from the group consisting of zirconium and titanium.
4. A method according to claim 3 wherein the liquid metal is bismuth.
References Cited in the file of this patent UNITED STATES PATENTS 2,437,249 Floe Mar. 9, 1948

Claims (1)

1. A METHOD OF INHIBITING CORROSION OF A FERROUS METAL PLATE CONTAINING NITROGEN AND HAVING A SURFACE IN CONTACT WITH A LIQUID METAL, COMPRISING ADDING TO THE LIQUID METAL AN ELEMENT WHICH COMBINES WITH THE NITROGEN IN THE FERROUS METAL PLATE TO FORM A CORROSION RESISTANT NITRIDE LAYER ON SAID SURFACE, CONTACTING THE OPPOSITE SURFACE OF THE FERROUS METAL PLATE WITH A MATERIAL WHICH FORMS A NITRIDE OF THE FERROUS METAL, AND MAINTAINING A LAYER OF THE FERROUS METAL NITRIDE ON SAID OPPOSITE SURFACE DURING THE TIME SAID LIQUID METAL IS IN CONTACT WITH THE FERROUS METAL PLATE, WHEREBY NITROGEN IONS MIGRATE FROM SAID OPPOSITE SURFACE TO SAID FIRST-NAMED SURFACE TO MAINTAIN THE NITRIDE LAYER ON SAID FIRST-NAMED SURFACE.
US746328A 1957-07-03 1958-07-03 Corrosion inhibition in ferrous metals Expired - Lifetime US2978368A (en)

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Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2437249A (en) * 1946-04-17 1948-03-09 Nitralloy Corp Method of nitriding

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2437249A (en) * 1946-04-17 1948-03-09 Nitralloy Corp Method of nitriding

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